1. Field of the Invention
The invention relates to an electronic package incorporating electronic components generating and/or receiving light-based (visible or invisible) signals and optical elements.
2. Related Art
The pattern within the last couple of years, for example for transistor packages irrespective of the TO header has been the use of window caps with Optical Sub Assembly (OSA), which has been improved by the use of ball lens caps in different materials like glass, sapphire, quartz, silicon etc. suiting the requirements. The next stage of performance improvement was achieved by using aspheric lenses, which eliminated the linear aberration of the focus limitation of ball lenses. All the optical materials were conveniently coated with different coatings serving the applications, for instance antireflective coating, beam splitter etc.
All the optical elements in such TO caps have been traditionally sealed by different sealing processes into metal caps, which were either machined, deep-drawn or manufactured by a similar manufacturing method. Other non-metallic materials like ceramics are also useable based upon their application, for example, in Hybrid packages. Sealing methods vary from user to user and can be glass-to-metal sealing, metallizing, soldering or any other process, which seals or glues the optical element to the cap or the hybrid housing. The cap can be made out of any material, such as metal, ceramic, plastic etc.
The cap with the optical element is mounted on, e.g. a transistor outline header or a hybrid package with optical window, both of which have an active or passive device needing packaging, and is sealed by a suitable method. The optical element acts as an important part of the current assembly, since in operation it functions to correctly channel the output of the device. The same applies for devices receiving light signals. The package could be hermetic, semi-hermetic or non-hermetic according to the requirements of the particular application.
Consideration is drawn to the packaging of a laser device for a transceiver application, in which a laser device is mounted on a TO header along with other required electronics. This laser device would require a hermetic packaging for longer lasting life along with optimal performance. The package is required to bring in electrical connections and feed the optical output from the device into a coupling object or device.
In most cases after the assembly of the device on the TO header is completed a TO cap with an optical element such as a ball lens is used. The ball lens is used to channel the output of the laser device into a fiber. The ball lens is usually sealed in the metal cap with glass solder or glass frit. This TO cap after assembly is then sealed onto the TO header with any suitable method, e.g. by seam welding or projection welding. Once the complete assembly of header and cap is finished, the device is started electrically and the output of the laser and an OSA is channeled into a fiber.
Such an electronic package is known from GB 2 360 656 A. This document discloses a transceiver using diffractive optical elements to direct the beams. The transceiver includes a transmitter for outputting a plurality of beams of electromagnetic energy. The transmitter is a vertical cavity surface emitting laser. An arrangement of diffractive optical elements (DOE's) directs a plurality of beams output by the transmitter to a detector. Preferably the optical elements are fabricated by imprinting a pattern high temperature film substrate using an ultraviolet epoxy. The use of a vertical cavity surface emitting laser is supposed to allow for high data rates while the diffractive optical element allows for a compact design. However, the design of the transceiver is still quite complicated and thus expensive. Nowadays requirements, however, are to manufacture electronic packages as cost-effectively as possible with the highest quality.